In some vehicles, gear position or range within the power train is shifted via a shift-by-wire or electronic transmission range selector. This device includes an actuator that shifts gears within the vehicle transmission and is controlled via a wired connection by a remote range selector operated by the vehicle user. Using the electronic transmission range selector, the vehicle user is able to change the transmission gear range between the several available gear ranges, including park, neutral, drive, reverse, etc. An electronic transmission range selector is advantageous compared to some conventional vehicle transmission range selectors that are controlled via a gear shift lever that is connected to the transmission via a mechanical linkage. For example, the electronic transmission range selector has a reduced space requirement within the vehicle compartment as compared to the conventional mechanical transmission range selector.
The actuator of the electronic transmission range selector may be an electric motor. In this case, it is important to be able to securely place the vehicle in the park transmission range in the event of an abnormality and/or failure occurs in the actuator power source (i.e., a vehicle battery), the electrical conductors that supply power to the actuator, or in the actuator itself.